Chemical conversion-treated metal plate

ABSTRACT

To provide a chemical conversion-treated metal sheet excellent in the corrosion resistance and coating adhesion, free from elution of chromium oxide and small in the environmental load, there is provided a chemical conversion-treated metal sheet comprising a metal sheet having on at least one surface thereof an inorganic film, wherein the inorganic film is a film comprising as a main component one or both of a metal oxide and a metal hydroxide exclusive of Cr and the film contains F.

TECHNICAL FIELD

The present invention relates to a chemical conversion-treated metalsheet having a small environmental load and an excellent corrosionresistance, which is used for automobiles, building materials, homeappliances and electric devices.

BACKGROUND ART

In the metal sheet used for automobiles, building materials, homeappliances and electric devices, a film comprising a chromium oxide isformed on the metal sheet surface to impart excellent corrosionresistance owing to the self-repairing function of the chromium oxideand thereby enhance the design property and corrosion resistance. Also,at the coating, a chromate treatment is applied as an undercoatingtreatment so as to enhance the corrosion resistance. However, from thestandpoint of protecting the global environment, it is recently requiredto prevent the elution of chromate oxide. Consequently, a chromium-freesurface film for the metal sheet or an undercoating treatment method notusing a chromate treatment is being demanded.

In order to satisfy these requirements, for example, a resin chromatefilm obtained by compounding an organic resin and a chromate has beenproposed in Japanese Unexamined Patent Publication (Kokai) No. 5-230666.However, this technique has a problem that the elution of chromium oxidecan be decreased but cannot be completely prevented.

On the other hand, a treatment technique not using a chromate has beenalso developed. For example, Japanese Unexamined Patent Publication(Kokai) No. 11-29724 discloses a method of covering the metal sheetsurface with a film comprising an aqueous resin having incorporatedtherein a thiocarbonyl group-containing compound, a phosphate ion and awater-dispersible silica. However, this technique has a problem thatalthough the corrosion resistance is improved, the adhesion of thecoating material is insufficient in uses where severe working isapplied.

Also, Japanese Unexamined Patent Publication (Kokai) No. 8-73775discloses an acidic surface treating agent containing two kinds ofsilane coupling agents. This technique has a problem that although goodadhesion of the coating material can be obtained, the corrosionresistance is not satisfied.

Under these circumstances, the present invention provides a chemicalconversion-treated metal sheet excellent in the corrosion resistance andcoating adhesion, free from elution of chromium oxide and small in theenvironmental load.

DISCLOSURE OF THE INVENTION

As a result of intensive investigations to solve the above-describedproblems, the present inventors have succeeded in providing a metalsheet excellent in the corrosion resistance and coating adhesion andfree from elution of chromium oxide by forming an inorganic filmcomprising an F-containing metal oxide or metal hydroxide (excluding Cr)on the metal surface. Incidentally, the present inventors have foundthat this metal sheet can be obtained by dipping a metal sheet in atreating aqueous solution containing, alone or as a composite, one ormore metal ion selected from Ti ion, Zr ion and Si ion and containingone or both of F ion and F-containing complex ion at a molar ratio of6.5 times or more to the metal ion, with the pH of the aqueous solutionbeing adjusted to 2 to 7, and if desired, when a metal sheet having onthe surface thereof a phase differing in the potential formed by adding,alone or as a composite, one or more ion selected from Zn ion, Al ion,Mg ion, Ni ion and Co ion is dipped in the above-described aqueoussolution, a high-quality chemical conversion-treated metal sheet can beeasily and simply obtained.

That is, the gist of the present invention is as follows.

(1) A chemical conversion-treated metal sheet comprising a metal sheethaving on at least one surface thereof an inorganic film, wherein theinorganic film is a film comprising as a main component one or both of ametal oxide and a metal hydroxide exclusive of Cr and the film containsF.

(2) The chemical conversion-treated metal sheet as described in (1)above, wherein the content of said one or both of a metal oxide and ametal hydroxide is 50 atom % or more based on said film exclusive of F.

(3) The chemical conversion-treated metal sheet as described in (1)above, wherein the content of said one or both of a metal oxide and ametal hydroxide is 80 atom % or more based on said film exclusive of F.

(4) The chemical conversion-treated metal sheet as described in (1)above, wherein the content of said one or both of a metal oxide and ametal hydroxide is 90 atom % or more based on said film exclusive of F.

(5) The chemical conversion-treated metal sheet as described in any oneof (1) to (4) above, wherein the content of F in said film is from 1atom % to less than 60 atom %.

(6) The chemical conversion-treated metal sheet as described in any oneof (1) to (4) above, wherein the content of F in said film is from 3atom % to 35 atom %.

(7) The chemical conversion-treated metal sheet as described in any oneof (1) to (4) above, wherein the content of F in said film is from 5atom % to 30 atom %.

(8) The chemical conversion-treated metal sheet as described in any oneof (1) to (7) above, wherein at least a part of the metal component ofsaid film has both a bond to O and a bond to F.

(9) The chemical conversion-treated metal sheet as described in any oneof (1) to (7) above, wherein the metal component of said film is one ormore member selected from the group consisting of Ti, Zr and Si.

(10) The chemical conversion-treated metal sheet as described in (9)above, wherein said film further contains, as an additional element, oneor more element selected from the group consisting of Mg, Al, Zn, Ni andCo.

(11) The chemical conversion-treated metal sheet as described in (10)above, wherein the content of the additional element in said film issuch that the Zn content is from 0.1 atom % to less than 50 atom %.

(12) The chemical conversion-treated metal sheet as described in (10) or(11) above, wherein the content of the additional element in said filmis such that the Al content is from 1 atom % to less than 30 atom %.

(13) The chemical conversion-treated metal sheet as described in any oneof (10) to (12) above, wherein the content of the additional element insaid film is such that the Mg content is from 1 atom % to less than 30atom %.

(14) The chemical conversion-treated metal sheet as described in any oneof (10) to (13) above, wherein the content of the additional element insaid film is such that the Ni content is from 1 atom % to less than 30atom %.

(15) The chemical conversion-treated metal sheet as described in any oneof (10) to (14) above, wherein the content of the additional element insaid film is such that the Co content is from 1 atom % to less than 30atom %.

(16) The chemical conversion-treated metal sheet as described in any oneof (10) to (15) above, wherein the additional element in said film has abond to 0 or F or both a bond to O and a bond to F.

BEST MODE FOR CARRYING OUT THE INVENTION

The chemical conversion-treated metal sheet of the present invention ischaracterized by being excellent in the corrosion resistance andadhesion of coating material, free from elution of chromium oxide andsmall in the environmental load. In order to impart these characteristicfeatures, in the present invention, a film mainly comprising one or bothof a metal oxide and a metal hydroxide (hereinafter called “a metaloxide or the like”) is formed on one surface or both surfaces of a metalsheet and F is incorporated into the film. It is considered that Fbonded to the metal component in the film is stronger in the action ofwithdrawing an electron than oxygen O bonded to the metal component andtherefore, a firmer film is obtained, as a result, the corrosionresistance and adhesion to a coating material are enhanced.

The expression “a film comprising one or both of a metal oxide and ametal hydroxide as a main component” means that the metal oxide andmetal hydroxide is contained in an amount of 50 atom % or more of thefilm excluding F. The preferred amount is 80 atom % or more, morepreferred amount is 90 atom % or more and particularly preferred amountis 95 atom % or more.

The amount of F contained in the film is preferably from 1 atom % toless than 60 atom % in terms of the component content in the film. Ifthe F content is less than 1 atom %, insufficient corrosion resistancemay result, whereas if the F content is 60 atom % or more, formation ofthe film mainly comprising a metal oxide or the like is inhibited. Thepreferred amount of F is 3 atom % to 35 atom %, more preferably from 5atom % to 30 atom %, particularly preferably 5 atom % to 20 atom %. Inorder to allow for formation of firm film and enhancement of corrosionresistance by the above-described action of F, the metal element in thefilm preferably has both a bond to O atom and a bond to F atom.

In the present invention, the film formed on the surface of a metalsheet preferably comprises one or both of an oxide and a hydroxide ofSi, Ti or Zr. These metal oxides and the like may be used individuallyor in combination of two or more thereof. The reason why Si, Ti and Zrare selected as the metal component of the film is because the metaloxide or the like thereof can form a film on the metal sheet surface ata low cost and the film is excellent in the corrosion resistance andadhesion to the metal sheet. In order to allow for formation of firmfilm and enhancement of corrosion resistance, Si, Ti or Zr is preferablyrendered to have both a bond to O and a bond to F in the film.

Furthermore, in the present invention, the film comprising theabove-described F-containing metal oxide or the like preferablycontains, as the additional element, one or more element selected fromZn, Al, Mg, Ni and Co. The content of the additional element ispreferably such that Zn is from 0.1 atom % to less than 50 atom %, morepreferably from 1 atom % to 20 atom %, Al is from 1 atom % to less than30 atom %, more preferably from 1 atom % to 20 atom %, Mg is from 1 atom% to less than 30 atom %, more preferably from 1 atom % to 15 atom %, Niis from 1 atom % to less than 30 atom %, more preferably from 1 atom %to 15 atom %, and Co is from 1 atom % to less than 30 atom %, morepreferably from 1 atom % to 15 atom %. Such an element is added to moreenhance the adhesion between the metal sheet and the film and if thecontent thereof is less than the specified range, the effect ofimproving the adhesion may not be obtained, whereas if addedexcessively, this highly probably gives rise to deterioration of thecorrosion resistance or increase in the production cost.

In the film, the additional element is preferably present in the stateof being bonded to O or F or bonded to both O and F, that is, Zn ispresent in the form of either Zn—O or Zn—F or in both of these bondingforms, Al is present in the form of either Al—O or Al—F or in both ofthese bonding forms, Mg is present in the form of either Mg—O or Mg—F orin both of these bonding forms, Ni is present in the form of either Ni—Oor Ni—F or in both of these bonding forms, and Co is present in the formof either Co—O or Co—F or in both of these bonding forms. The elementsadded each can be stably present in the film by taking such a bondingform and the corrosion resistance of the metal sheet is more enhanced.

The chemical conversion-treated metal sheet of the present invention isnot particularly limited in its production method as long as a filmstructure specified in the present invention can be obtained, and may beproduced by a vapor phase process such as sputtering and CVD or by asol-gel process widely employed as the production method of an oxidefilm.

Also, in the production of the chemical conversion-treated metal sheetof the present invention, when a liquid phase deposition process usingan aqueous solution of an F compound such as fluoro-complex ion is used,the production cost can be made low because of no use of an expensivevacuum evacuation system required in the vapor phase process and,furthermore, the measure for the formation of voids in the filmresulting from generation of volatile components in the firing step,which occurs in forming a film by a sol-gel process, is not necessary.In addition, it is considered that according to the liquid phasedeposition process, the film formed on the surface of the chemicalconversion-treated metal sheet of the present invention comprises thebasic unit having a structure where a metal is bonded with oxygenstherearound and these basic units are bonded to each other, and when thefilm contains F, the basic units are arrayed to give a dense film.

The method for producing the chemical conversion-treated metal sheet ofthe present invention by the above-described liquid phase depositionprocess using an aqueous fluorine compound solution is described below.

An aqueous solution of an F compound where a metal element as thecomponent of the film and F are compounded is prepared and used as thetreating solution. More specifically, a treating aqueous solutioncontaining, alone or as a composite, one or more metal element selectedfrom Ti ion, Zr ion and Si ion and containing one or both of F ion andF-containing complex ion at a molar ratio of 6.5 times or more to themetal ion is adjusted to a pH of 2 to 7 and if desired, one or more ionselected from Zn ion, Al ion, Mg ion, Ni ion and Co ion is added aloneor as a composite to the aqueous solution to prepare a treatingsolution.

When a metal sheet to be treated is dipped in this treating solution, atleast one reaction out of the consumption of F ion and the reduction ofH ion takes place, a reaction of converting a metal ion into a metaloxide or the like proceeds, and the metal oxide or the like deposit onthe metal sheet surface. When the metal sheet to be treated has on thesurface thereof a phase differing in the potential, such as aluminumalloy or zinc-aluminum alloy plating sheet, local cells are formedbetween the phases, as a result, the F ion consumption reaction and Hion reduction reaction efficiently occur and the deposition rateincreases. In addition to such mere dipping, when the metal sheet to betreated is short-circuited with a metal material having a standardelectrode potential lower than that of the metal sheet, an anodereaction takes place only on the metal material having a low standardelectrode potential and therefore, the metal oxide or the like can bemore efficiently deposited on the metal sheet. Also, when an insolublematerial and a metal sheet to be treated are dipped in theabove-described treating solution and a hydrogen ion reduction reactionis caused to proceed on the metal sheet while controlling the insolublematerial to undertake an anodic reaction and the metal sheet toundertake a cathodic reaction, the oxide or hydroxide can be depositedon the meal sheet due to elevation of the interface pH along theprogress of the reduction reaction. By controlling the hydrogengenerating reaction and the elevation of interface pH within the rangeof not inhibiting the film formation, the deposition rate can beincreased. As for the consumption of fluorine ion, boron ion or aluminumion for forming a stable fluoride may be added to the treating solution.When the potential is controlled to an extent of not bringing aboutdeposition reaction inhibition due to generation of hydrogen gas, auniform film can be formed within a short time. The control of potentialcan be facilitated by setting the bath pH to an appropriate range,because if the pH of the treating solution is too low, a vigoroushydrogen reduction reaction readily occurs. In other words, thedeposition rate can be increased by controlling the hydrogen generatingreaction. Therefore, the pH of the treating solution is adjusted to 2 to7.

In an aqueous solution where metal ion and fluorine ion in a molar ratioof 4 times or more to the metal ion are present together, and/or in anaqueous solution containing a complex ion comprising a metal andfluorine in a molar ratio of 4 times or more to the metal, anequilibrium reaction involving the fluorine ion occurs between the metalion and one or both of an oxide and a hydroxide. As the fluorine ion orhydrogen ion is consumed or reduced, a reaction of converting the metalion into one or both of an oxide and a hydroxide proceeds. In thisreaction, when the F ion content in the aqueous solution is set to 6.5times or more the content of the metal ion, the F ion is taken into oneor both of an oxide and a hydroxide, and a bond connecting the metal ionto F atom and a bond connecting the meal ion to O atom can be formed inthe film.

The deposition very slowly proceeds only by the operation of dipping themetal sheet to be treated in a treating solution, but when an insolubleelectrode is dipped in the treating solution and a cathode overvoltageof several mV to hundreds of mV is applied to a substrate on which themetal oxide or the like are intended to deposit, the deposition rate isremarkably increased. At this time, a very homogeneous film is formed onthe surface of the metal sheet to be treated, though a hydrogen gas isgenerated. If the pH of the treating solution is rendered to be lower soas to accelerate the generation of this gas, a film may not be formed ora film having a non-uniform thickness or a poor adhesive strength mayresult. From these reasons, the pH of the treating solution ispreferably from 2 to 7, more preferably from 3 to 4. If the pH of thetreating solution is less than 2, the film formation is readilyinhibited due to generation of hydrogen and the potential control forsound film formation becomes difficult, whereas if the pH of thetreating solution exceeds 7, the solution is unstable or an aggregatemay be deposited to give an insufficient adhesive strength.

If the molar ratio of fluorine ion to the metal ion in the treatingsolution is less than 4 times, a film may not be deposited or ifdeposited, very little. By setting the molar ratio of fluorine ion tothe metal ion in the treating solution to 6.5 times or more, thefluorine ion in the treating solution is taken into an oxide of the filmin the process of depositing the film and a fluorine-containing filmcomprising one or both of a metal oxide and a metal hydroxide is formed.

The metal sheet to which the present invention is applied is notparticularly limited but, for example, the present invention can be usedfor enhancing the corrosion resistance of a steel sheet, a stainlesssteel sheet, an aluminum alloy sheet, a copper sheet or a metal sheethaving a plated surface. Also, when the film is used as an undercoatingfilm of a coated steel sheet and the like, the corrosion resistance andthe adhesion between resin and metal can be enhanced.

Examples of the stainless steel sheet include ferrite stainless steelsheet, martensite stainless steel sheet and austenite stainless steelsheet. Examples of the aluminum sheet and aluminum alloy sheet includeJIS1000 series (pure Al type), JIS2000 series (Al—Cu type), JIS3000series (Al—Mn type), JIS4000 series (Al—Si type), JIS5000 series (Al—Mgtype), JIS6000 series (Al—Mg—Si type) and JIS7000 series (Al—Zn type).Examples of the plated steel sheet include Zn-plated steel sheet,Ni-plated steel sheet, Sn-plated steel sheet, Zn—Fe alloy-plated steelsheet and Zn—Ni alloy-plated steel sheet. Examples of the metal sheethaving on the surface thereof a phase differing in the potential includealuminum alloy sheet, Zn—Al alloy-plated steel sheet, Zn—Al—Mg alloyplated steel sheet, Zn—Al—Mg—Si alloy-plated steel sheet, Al—Sialloy-plated sheet and Al—Zn—Si alloy-plated sheet. Also, coating may beapplied to the chemical conversion-treated metal sheet of the presentinvention.

EXAMPLE

The present invention is described in greater detail below by referringto Example, but the present invention is not limited to this Example.

The metal sheet used were hot-dip galvanized steel sheet (platingcoverage on both surfaces: 100 g/m²) and stainless steel sheet (SUS304),and the metal sheet having on the surface thereof a phase differing inthe potential used were a hot-dip 55% Al-43.4% Zn-1.6% Si alloy-platedsteel sheet (plating coverage on both surfaces: 150 g/m ²), a Zn-11%Al-3% Mg-0.2% Si alloy-plated steel sheet (plating coverage on bothsurfaces: 120 g/m²) and an aluminum alloy sheet (JIS A 3005 (Al—Mntype)). These metal sheets all had a thickness of 0.8 mm. Each metalsheet sample was subjected to an alkali degreasing treatment and then tothe tests described below.

A metal oxide and a metal hydroxide were formed on the surface of eachmetal sheet by a liquid phase process.

The treating solutions used in the liquid phase process were

an aqueous 0.1 mol/L ammonium hexafluorosilicate solution (treatingsolution (1)),

an aqueous 0.1 mol/L ammonium hexafluorotitanate solution (treatingsolution (2)),

an aqueous 0.1 mol/L ammonium hexafluorozirconate solution (treatingsolution (3)),

a mixed aqueous solution of an aqueous 0.05 mol/L ammoniumhexafluorotitanate solution and an aqueous 0.05 mol/L ammoniumhexafluorosilicate solution (treating solution (4)),

a mixed aqueous solution of an aqueous 0.05 mol/L ammoniumhexafluorotitanate solution and an aqueous 0.05 mol/L ammoniumhexafluorozirconate solution (treating solution (5)),

a mixed aqueous solution of an aqueous 0.05 mol/L ammoniumhexafluorozirconate solution and an aqueous 0.05 mol/L ammoniumhexafluorosilicate solution (treating solution (6)),

a mixed aqueous solution of an aqueous 0.03 mol/L ammoniumhexafluorotitanate solution, an aqueous 0.03 mol/L ammoniumhexafluorosilicate solution and an aqueous 0.03 mol/L ammoniumhexafluorozirconate solution (treating solution (7)),

a mixed aqueous solution of an aqueous 0.1 mol/L ammoniumhexafluorosilicate solution and an aqueous 0.01 mol/L zinc chloridesolution (treating solution (8)),

a mixed aqueous solution of an aqueous 0.1 mol/L ammoniumhexafluorotitanate solution and an aqueous 0.01 mol/L zinc chloridesolution (treating solution (9)),

a mixed aqueous solution of an aqueous 0.1 mol/L ammoniumhexafluorozirconate solution and an aqueous 0.01 mol/L zinc chloridesolution (treating solution (10)),

a mixed aqueous solution of an aqueous 0.1 mol/L ammoniumhexafluorosilicate solution and an aqueous 0.01 mol/L magnesium chloridesolution (treating solution (11)),

a mixed aqueous solution of an aqueous 0.1 mol/L ammoniumhexafluorotitanate solution and an aqueous 0.01 mol/L magnesium chloridesolution (treating solution (12)),

a mixed aqueous solution of an aqueous 0.1 mol/L ammoniumhexafluorozirconate solution and an aqueous 0.01 mol/L magnesiumchloride solution (treating solution (13)),

a mixed aqueous solution of an aqueous 0.1 mol/L ammoniumhexafluorosilicate solution and an aqueous 0.01 mol/L aluminum chloridesolution (treating solution (14)),

a mixed aqueous solution of an aqueous 0.1 mol/L ammoniumhexafluorotitanate solution and an aqueous 0.01 mol/L aluminum chloridesolution (treating solution (15)),

a mixed aqueous solution of an aqueous 0.1 mol/L ammoniumhexafluorozirconate solution and an aqueous 0.01 mol/L aluminum chloridesolution (treating solution (16)),

a mixed aqueous solution of an aqueous 0.1 mol/L ammoniumhexafluorosilicate solution and an aqueous 0.01 mol/L nickel chloridesolution (treating solution (17)),

a mixed aqueous solution of an aqueous 0.1 mol/L ammoniumhexafluorotitanate solution and an aqueous 0.01 mol/L nickel chloridesolution (treating solution (18)),

a mixed aqueous solution of an aqueous 0.1 mol/L ammoniumhexafluorozirconate solution and an aqueous 0.01 mol/L nickel chloridesolution (treating solution (19)),

a mixed aqueous solution of an aqueous 0.1 mol/L ammoniumhexafluorosilicate solution and an aqueous 0.01 mol/L cobalt chloridesolution (treating solution (20)),

a mixed aqueous solution of an aqueous 0.1 mol/L ammoniumhexafluorotitanate solution and an aqueous 0.01 mol/L cobalt chloridesolution (treating solution (21)), and

a mixed aqueous solution of an aqueous 0.1 mol/L ammoniumhexafluorozirconate solution and an aqueous 0.01 mol/L cobalt chloridesolution (treating solution (22)).

The treating solutions (1) to (7) were adjusted by mainly using ammoniumfluoride and further, if desired, hydrofluoric acid or aqueous ammoniain the aqueous hexafluoro-complex salt solution such that the molarratio of metal to entire fluorine was about 1:6.5 and the pH was about3. The treating solutions (8) to (22) were adjusted, after adding thechloride to the aqueous hexafluoro-complex salt solution, by mainlyusing ammonium fluoride and further, if desired, hydrofluoric acid oraqueous ammonia such that the molar ratio of metal species ofhexafluoro-complex salt to entire fluorine was about 1:6.5 and the pHwas about 3.

Each degreased metal sheet was dipped in the treating solution and afilm of metal oxide and metal hydroxide was formed on the metal sheet bycathodic electrolysis using a platinum as the counter electrode. Thefilm formation was performed at room temperature for 5 minutes bycontrolling the current density to 100 mA/cm² and after the filmformation, the metal sheet was washed with water and dried. In thesamples using treating solutions (1) to (7), the fluorine ion in thetreating solution was taken into an oxide of the film in the process ofdepositing the film and a fluorine-containing metal oxide or metalhydroxide film was formed. In the samples using treating solutions (8)to (22), the metal ion and fluorine ion in the mixed aqueous solutionwere taken into the film and a metal oxide or metal hydroxide filmcontaining an additional element and fluorine were formed.

As for the degreased-hot-dip 55% Al-43.4% Zn-1.6% Si alloy-plated steelsheet and Zn-11% Al-3% Mg-0.2% Si alloy-plated steel sheet, the filmformation was performed also by a so-called dipping process of dippingthe metal sheet in the treating solution (1), (2) or (3) for 7 minutesand after film formation, water-washing and drying it. In this case, ametal oxide or metal hydroxide film having taken thereinto the fluorineion in the treating solution and a metal ion considered to havedissolved out due to formation of local cells was formed.

For the purpose of comparison, a film comprising only SiO₂, TiO₂ or ZrO₂was formed on the metal sheet by a sputtering process using SiO₂, TiO₂or ZrO₂ as the target, respectively.

These films formed by the above-described liquid phase process or vaporphase process each was subjected to determination of amounts of elementscontained in the film by the X-ray photoelectric spectroscopy. Also, thebonded state of the additional elements in the film was estimated fromthe chemical shift on the photoelectric spectrum of each elementdetermined by the X-ray photoelectric spectroscopy. Furthermore, metalatoms, F atom, O atom and peripheral fine structure were examined by theXAFS (X-ray absorption fine-structures) method and each bonded state wasestimated.

Out of the thus-produced various chemical conversion-treated metalsheets, the naked corrosion resistance of the hot-dip galvanized steelsheet was evaluated by performing a continuous salt spray test for 500hours according to JIS Z 2371. The rust generated was rated AA when thewhite rust generation ratio was 5% or less, rated BB when the white rustgeneration ratio was from 5% to 10% or less, rated CC when the red rustgeneration ratio was 5% or less, and rated DD when the red rustgeneration ratio was more than 5%. Samples rated BB or higher (AA) werejudged good. Other metal sheets were not subjected to the evaluation ofnaked corrosion resistance by a continuous salt spray test, because themetal sheets themselves had good corrosion resistance.

Also, the obtained various chemical conversion-treated metal sheets eachwas coated under the following conditions to make a coated metal sheet.First, an epoxy-based primer coating material (P655, produced by NipponFine Coatings K.K.) using a chromate-free rust-preventive pigment wascoated as the primer-coating material to a dry film thickness of 5 μmand further thereon, a high molecular polyester-based coating material(NSC200HQ, produced by Nippon Fine Coatings K.K.) was coated to a dryfilm thickness of 15 μm. These coated metal sheets were evaluated on thecoating material adhesion and corrosion resistance under the followingconditions.

1) Coating Material Adhesion

The clear coated metal sheet produced by the above-described method wasdipped in boiling water for 60 minutes. Thereafter, crosscuts wereformed thereon according to the crosscut test method described in JIS K5400 and further an Erichsen process of 7 mm was applied. Apressure-sensitive adhesive tape (cellophane tape produced by NichibanCo., Ltd.) was laminated on the processed part and then swiftly peeledoff by pulling it toward the oblique direction of 45°, and the number ofpeeled crosscuts out of 100 crosscuts was counted. The adhesion wasevaluated on a 5-stage scale according to the peeling criteria shown inTable 1 and scores of 3 or higher were ranked as “passed”.

TABLE 1 Score Rating Criteria of Coating Material Adhesion 5 No peeling4 Peeled area ratio of less than 5% 3 Peeled area ratio of 5% to lessthan 20% 2 Peeled area ratio of 20% to less than 70% 1 Peeled area ratioof 70% or more2) Coating Corrosion Resistance Test

A sample for coating corrosion resistance test was prepared by cuttingthe right and left cut-end faces into an upper flash and a lower flashand according to the neutral salt spray cycle test described in JIS H8502, 180 cycles were performed with one cycle consisting of spraying ofan aqueous 5 wt % NaCl solution (2 hours)→drying (60° C., RH: 20 to 30%,4 hours)→wetting (50° C., RH: 95% or more). The maximum blister widthfrom the cut end face part was evaluated. The samples were rated on a5-stage scale according to the blister width criteria shown in Table 2and scores of 3 or higher were ranked as “passed”.

TABLE 2 Score Rating Criteria of Corrosion Resistance 5 No blister 4Maximum blister width of less than 3 mm 3 Maximum blister width of 3 mmto less than 5 mm 2 Maximum blister width of 5 mm to less than 7 mm 1Maximum blister width of 7 mm or more

Samples passed both the coating material adhesion test and the corrosionresistance test were judged good.

TABLE 3 Evaluation Results of Hot-Dip Galvanized Steel Sheet TreatingContent of Additional Solution of Target of Element in Film NakedCoating Liquid Phase Vapor Phase (atom % by number) Corrosion CoatingCorrosion Film Formation Method Process Process F Mg Al Zn Ni CoResistance Adhesion Resistance Remarks liquid phase process (1) — 5 0 00 0 0 BB passed passed Invention (cathodic electrolysis) liquid phaseprocess (2) — 10 0 0 0 0 0 BB passed passed Invention (cathodicelectrolysis) liquid phase process (3) — 30 0 0 0 0 0 BB passed passedInvention (cathodic electrolysis) liquid phase process (4) — 5 0 0 0 0 0BB passed passed Invention (cathodic electrolysis) liquid phase process(5) — 10 0 0 0 0 0 BB passed passed Invention (cathodic electrolysis)liquid phase process (6) — 30 0 0 0 0 0 BB passed passed Invention(cathodic electrolysis) liquid phase process (7) — 20 0 0 0 0 0 BBpassed passed Invention (cathodic electrolysis) liquid phase process (8)— 5 0 0 20 0 0 AA passed passed Invention (cathodic electrolysis) liquidphase process (9) — 10 0 0 20 0 0 AA passed passed Invention (cathodicelectrolysis) liquid phase process (10) — 30 0 0 20 0 0 AA passed passedInvention (cathodic electrolysis) liquid phase process (11) — 5 10 0 0 00 AA passed passed Invention (cathodic electrolysis) liquid phaseprocess (12) — 10 10 0 0 0 0 AA passed passed Invention (cathodicelectrolysis) liquid phase process (13) — 30 10 0 0 0 0 AA passed passedInvention (cathodic electrolysis) liquid phase process (14) — 5 0 15 0 00 AA passed passed Invention (cathodic electrolysis) liquid phaseprocess (15) — 10 0 15 0 0 0 AA passed passed Invention (cathodicelectrolysis) liquid phase process (16) — 30 0 15 0 0 0 AA passed passedInvention (cathodic electrolysis) liquid phase process (17) — 5 0 0 0 20 BB passed passed Invention (cathodic electrolysis) liquid phaseprocess (18) — 10 0 0 0 2 0 BB passed passed Invention (cathodicelectrolysis) liquid phase process (19) — 30 0 0 0 2 0 BB passed passedInvention (cathodic electrolysis) liquid phase process (20) — 5 0 0 0 02 BB passed passed Invention (cathodic electrolysis) liquid phaseprocess (21) — 10 0 0 0 0 2 BB passed passed Invention (cathodicelectrolysis) liquid phase process (22) — 30 0 0 0 0 2 BB passed passedInvention (cathodic electrolysis) vapor phase process — SiO₂ 0 0 0 0 0 0CC not passed not passed Comparison vapor phase process — TiO₂ 0 0 0 0 00 DD not passed not passed Comparison vapor phase process — ZrO₂ 0 0 0 00 0 DD not passed not passed Comparison

TABLE 4 Evaluation Results of 55% Al—43.3% Zn—1.6% Si Alloy-Plated SteelSheet Treating Content of Additional Solution of Target of Element inFilm Coating Liquid Phase Vapor Phase (atom % by number) CoatingCorrosion Film Formation Method Process Process F Mg Al Zn Ni CoAdhesion Resistance Remarks liquid phase process (1) — 5 0 0 0 0 0passed passed Invention (cathodic electrolysis) liquid phase process (2)— 10 0 0 0 0 0 passed passed Invention (cathodic electrolysis) liquidphase process (3) — 30 0 0 0 0 0 passed passed Invention (cathodicelectrolysis) liquid phase process (4) — 5 0 0 0 0 0 passed passedInvention (cathodic electrolysis) liquid phase process (5) — 10 0 0 0 00 passed passed Invention (cathodic electrolysis) liquid phase process(6) — 30 0 0 0 0 0 passed passed Invention (cathodic electrolysis)liquid phase process (7) — 20 0 0 0 0 0 passed passed Invention(cathodic electrolysis) liquid phase process (1) — 5 0 5 5 0 0 passedpassed Invention (dipping) liquid phase process (2) — 10 0 5 5 0 0passed passed Invention (dipping) liquid phase process (3) — 30 0 5 5 00 passed passed Invention (dipping) vapor phase process — SiO₂ 0 0 0 0 00 not passed not passed Comparison vapor phase process — TiO₂ 0 0 0 0 00 not passed not passed Comparison vapor phase process — ZrO₂ 0 0 0 0 00 not passed not passed Comparison

TABLE 5 Evaluation Results of Zn—11% Al—3% Mg—0.2% Si Alloy-Plated SteelSheet Treating Content of Additional Solution of Target of Element inFilm Coating Liquid Phase Vapor Phase (atom % by number) CoatingCorrosion Film Formation Method Process Process F Mg Al Zn Ni CoAdhesion Resistance Remarks liquid phase process (17) — 5 0 0 0 2 0passed passed Invention (cathodic electrolysis) liquid phase process(18) — 10 0 0 0 2 0 passed passed Invention (cathodic electrolysis)liquid phase process (19) — 30 0 0 0 2 0 passed passed Invention(cathodic electrolysis) liquid phase process (20) — 5 0 0 0 0 2 passedpassed Invention (cathodic electrolysis) liquid phase process (21) — 100 0 0 0 2 passed passed Invention (cathodic electrolysis) liquid phaseprocess (22) — 30 0 0 0 0 2 passed passed Invention (cathodicelectrolysis) liquid phase process (1) — 5 0 2 5 0 0 passed passedInvention (dipping) liquid phase process (2) — 10 0 2 5 0 0 passedpassed Invention (dipping) liquid phase process (3) — 30 0 2 5 0 0passed passed Invention (dipping) vapor phase process — SiO₂ 0 0 0 0 0 0not passed not passed Comparison vapor phase process — TiO₂ 0 0 0 0 0 0not passed not passed Comparison vapor phase process — ZrO₂ 0 0 0 0 0 0not passed not passed Comparison

TABLE 6 Evaluation Results of Aluminum Alloy Sheet Treating Content ofAdditional Solution of Target of Element in Film Coating Liquid PhaseVapor Phase (atom % by number) Coating Corrosion Film Formation MethodProcess Process F Mg Al Zn Ni Co Adhesion Resistance Remarks liquidphase process (8) — 5 0 0 20 0 0 passed passed Invention (cathodicelectrolysis) liquid phase process (9) — 10 0 0 20 0 0 passed passedInvention (cathodic electrolysis) liquid phase process (10)  — 30 0 0 200 0 passed passed Invention (cathodic electrolysis) vapor phase process— SiO₂ 0 0 0 0 0 0 not passed not passed Comparison vapor phase process— TiO₂ 0 0 0 0 0 0 not passed not passed Comparison vapor phase process— ZrO₂ 0 0 0 0 0 0 not passed not passed Comparison

TABLE 7 Evaluation Results of Stainless Steel Sheet Treating Content ofAdditional Solution of Target of Element in Film Coating Liquid PhaseVapor Phase (atom % by number) Coating Corrosion Film Formation MethodProcess Process F Mg Al Zn Ni Co Adhesion Resistance Remarks liquidphase process (11) — 5 10 0 0 0 0 passed passed Invention (cathodicelectrolysis) liquid phase process (12) — 10 10 0 0 0 0 passed passedInvention (cathodic electrolysis) liquid phase process (13) — 30 10 0 00 0 passed passed Invention (cathodic electrolysis) liquid phase process(14) — 5 0 15 0 0 0 passed passed Invention (cathodic electrolysis)liquid phase process (15) — 10 0 15 0 0 0 passed passed Invention(cathodic electrolysis) liquid phase process (16) — 30 0 15 0 0 0 passedpassed Invention (cathodic electrolysis) vapor phase process — SiO₂ 0 00 0 0 0 not passed not passed Comparison vapor phase process — TiO₂ 0 00 0 0 0 not passed not passed Comparison vapor phase process — ZrO₂ 0 00 0 0 0 not passed not passed Comparison

The evaluations results in the above-described tests are shown in Tables3 to 7 every each metal sheet. It is apparent that the naked corrosionresistance, coating film adhesion and coating film corrosion resistanceall are improved by the present invention.

INDUSTRIAL APPLICABILITY

According to the present invention, a chemical conversion-treated metalsheet excellent in the corrosion resistance and adhesion of coating filmand small in the environmental load can be provided even without using achromium-containing film, which is industrially useful.

1. A chemical conversion-treated metal sheet comprising a metal sheethaving on at least one surface thereof an inorganic film, wherein saidinorganic film is a film having a metal component, said inorganic filmcomprising one or both of a metal oxide and a metal hydroxide, and saidfilm containing F bonded to the metal of the metal component, said filmcontaining no Cr, said one or both of said metal oxide and metalhydroxide comprising 50 atom % or more of all atoms in said film aftersubtracting all said F atoms from said film, and F content in said filmis from 1 atom % to less than 60 atom % based on all atoms in said film;and at least a part of the metal component of said film has both achemical bond to O and a chemical bond to F.
 2. The chemicalconversion-treated metal sheet as claimed in claim 1, wherein thecontent of said one or both of said metal oxide and said metal hydroxideis 80 atom % or more of all atoms in said film after subtracting all Fatoms from said film.
 3. The chemical conversion-treated metal sheet asclaimed in claim 1, wherein the content of said one or both of saidmetal oxide and said metal hydroxide is 90 atom % or more of all atomsin said film after subtracting all F atoms from said film.
 4. Thechemical conversion-treated metal sheet as claimed in claim 1, whereinthe content of F in said film is from 3 atom % to 35 atom % based on allatoms in said film.
 5. The chemical conversion-treated metal sheet asclaimed in claim 1, wherein the content of F in said film is from 5 atom% to 30 atom % based on all atoms in said film.
 6. The chemicalconversion-treated metal sheet as claimed in claim 1, wherein the metalcomponent of said film is one or more member selected from the groupconsisting of Ti, Zr and Si.
 7. The chemical conversion-treated metalsheet as claimed in claim 6, wherein said film further contains, as anadditional element, one or more element selected from the groupconsisting of Mg, Al, Zn, Ni and Co.
 8. The chemical conversion-treatedmetal sheet as claimed in claim 7, wherein the content of the additionalelement in said film is such that the Zn content is from 0.1 atom % toless than 50 atom % based on all atoms in said film.
 9. The chemicalconversion-treated metal sheet as claimed in claim 7, wherein thecontent of the additional element in said film is such that the Alcontent is from 1 atom % to less than 30 atom % based on all atoms insaid film.
 10. The chemical conversion-treated metal sheet as claimed inclaim 7, wherein the content of the additional element in said film issuch that the Mg content is from 1 atom % to less than 30 atom % basedon all atoms in said film.
 11. The chemical conversion-treated metalsheet as claimed in claim 7, wherein the content of the additionalelement in said film is such that the Ni content is from 1 atom % toless than 30 atom % based on all atoms in said film.
 12. The chemicalconversion-treated metal sheet as claimed in claim 7, wherein thecontent of the additional element in said film is such that the Cocontent is from 1 atom % to less than 30 atom % based on all atoms insaid film.
 13. The chemical conversion-treated metal sheet as claimed inclaim 7, wherein each additional element in said film has a bond to O orF or both a bond to O and a bond to F.